/*******************************************************************************
 * Copyright (c) 2008 Standards for Technology in Automotive Retail and others
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     David Carver - STAR - initial API based off XMLTemplateCompletionProcessor
 *     
 *******************************************************************************/
package org.eclipse.wst.xml.xpath.ui.internal.contentassist;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.IRegion;
import org.eclipse.jface.text.ITextSelection;
import org.eclipse.jface.text.ITextViewer;
import org.eclipse.jface.text.Region;
import org.eclipse.jface.text.contentassist.ICompletionProposal;
import org.eclipse.jface.text.templates.ContextTypeRegistry;
import org.eclipse.jface.text.templates.Template;
import org.eclipse.jface.text.templates.TemplateCompletionProcessor;
import org.eclipse.jface.text.templates.TemplateContext;
import org.eclipse.jface.text.templates.TemplateContextType;
import org.eclipse.jface.text.templates.TemplateException;
import org.eclipse.jface.text.templates.TemplateProposal;
import org.eclipse.jface.text.templates.persistence.TemplateStore;
import org.eclipse.swt.graphics.Image;
import org.eclipse.wst.xml.ui.internal.contentassist.ReplaceNameTemplateContext;
import org.eclipse.wst.xml.xpath.ui.internal.XPathUIPlugin;
import org.eclipse.wst.xml.xpath.ui.internal.templates.TemplateContextTypeIdsXPath;
import org.eclipse.wst.xml.xpath.ui.internal.util.XPathPluginImageHelper;
import org.eclipse.wst.xml.xpath.ui.internal.util.XPathPluginImages;

/**
 * Completion processor for XML Templates. Most of the work is already done by
 * the XML Content Assist processor, so by the time the
 * XMLTemplateCompletionProcessor is asked for content assist proposals, the XML
 * content assist processor has already set the context type for templates.
 */
public class XPathTemplateCompletionProcessor extends
		TemplateCompletionProcessor {
	private static final class ProposalComparator implements Comparator,
			Serializable {

		private static final long serialVersionUID = 1686588609390747536L;

		public int compare(Object o1, Object o2) {
			return ((TemplateProposal) o2).getRelevance()
					- ((TemplateProposal) o1).getRelevance();
		}
	}

	private static final Comparator fgProposalComparator = new ProposalComparator();
	private String fContextTypeId = null;

	/*
	 * Copied from super class except instead of calling createContext(viewer,
	 * region) call createContext(viewer, region, offset) instead
	 */
	public ICompletionProposal[] computeCompletionProposals(ITextViewer viewer,
			int offset) {

		ITextSelection selection = (ITextSelection) viewer
				.getSelectionProvider().getSelection();

		// adjust offset to end of normalized selection
		if (selection.getOffset() == offset) {
			offset = selection.getOffset() + selection.getLength();
		}

		String prefix = extractPrefix(viewer, offset);
		Region region = new Region(offset - prefix.length(), prefix.length());
		TemplateContext context = createContext(viewer, region, offset);
		if (context == null) {
			return new ICompletionProposal[0];
		}

		// name of the selection variables {line, word}_selection
		context.setVariable("selection", selection.getText()); //$NON-NLS-1$

		Template[] templates = getTemplates(context.getContextType().getId());

		List matches = new ArrayList();
		for (int i = 0; i < templates.length; i++) {
			Template template = templates[i];
			try {
				context.getContextType().validate(template.getPattern());
			} catch (TemplateException e) {
				continue;
			}
			if (template.matches(prefix, context.getContextType().getId())) {
				matches.add(createProposal(template, context, (IRegion) region,
						getRelevance(template, prefix)));
			}
		}

		Collections.sort(matches, fgProposalComparator);

		return (ICompletionProposal[]) matches
				.toArray(new ICompletionProposal[matches.size()]);
	}

	/**
	 * Creates a concrete template context for the given region in the document.
	 * This involves finding out which context type is valid at the given
	 * location, and then creating a context of this type. The default
	 * implementation returns a <code>SmartReplaceTemplateContext</code> for the
	 * context type at the given location. This takes the offset at which
	 * content assist was invoked into consideration.
	 * 
	 * @param viewer
	 *            the viewer for which the context is created
	 * @param region
	 *            the region into <code>document</code> for which the context is
	 *            created
	 * @param offset
	 *            the original offset where content assist was invoked
	 * @return a template context that can handle template insertion at the
	 *         given location, or <code>null</code>
	 */
	private TemplateContext createContext(ITextViewer viewer, IRegion region,
			int offset) {
		// pretty much same code as super.createContext except create
		// SmartReplaceTemplateContext
		TemplateContextType contextType = getContextType(viewer, region);
		if (contextType != null) {
			IDocument document = viewer.getDocument();
			return new ReplaceNameTemplateContext(contextType, document, region
					.getOffset(), region.getLength(), offset);
		}
		return null;
	}

	protected ICompletionProposal createProposal(Template template,
			TemplateContext context, IRegion region, int relevance) {
		return new CustomTemplateProposal(template, context, region,
				getImage(template), relevance);
	}

	protected TemplateContextType getContextType(ITextViewer viewer,
			IRegion region) {
		TemplateContextType type = null;

		ContextTypeRegistry registry = getTemplateContextRegistry();
		if (registry != null) {
			type = registry.getContextType(fContextTypeId);
		}

		return type;
	}

	protected Image getImage(Template template) {
		if (TemplateContextTypeIdsXPath.AXIS
				.equals(template.getContextTypeId())) {
			return XPathPluginImageHelper.getInstance().getImage(
					XPathPluginImages.IMG_XPATH_AXIS);
		}

		if (TemplateContextTypeIdsXPath.XPATH.equals(template
				.getContextTypeId())) {
			return XPathPluginImageHelper.getInstance().getImage(
					XPathPluginImages.IMG_XPATH_FUNCTION);
		}

		if (TemplateContextTypeIdsXPath.OPERATOR.equals(template
				.getContextTypeId())) {
			return XPathPluginImageHelper.getInstance().getImage(
					XPathPluginImages.IMG_OPERATOR);
		}

		return null;
	}

	private ContextTypeRegistry getTemplateContextRegistry() {
		return XPathUIPlugin.getDefault().getXPathTemplateContextRegistry();
	}

	protected Template[] getTemplates(String contextTypeId) {
		Template templates[] = null;

		TemplateStore store = getTemplateStore();
		if (store != null) {
			templates = store.getTemplates(contextTypeId);
		}

		return templates;
	}

	private TemplateStore getTemplateStore() {
		return XPathUIPlugin.getDefault().getXPathTemplateStore();
	}

	public void setContextType(String contextTypeId) {
		fContextTypeId = contextTypeId;
	}
}